1. Field of the Invention
The present invention relates to a technique for performing different operations (electrical write operation of chip IDs, for example) depending on the chip position in the wafer surface, for each of chips cut from one wafer.
2. Description of Related Art
In order to enable to identify the position in the wafer surface where a semiconductor integrated circuit (chip) is formed therefrom, a chip ID is provided to each chip. The chip ID is provided to each chip by recording the position information in the wafer surface to PROM (Programmable Read Only Memory) formed in the chip, for example. If a fuse ROM is used as PROM, fuse elements (or anti-fuse elements) formed in each chip are selectively disconnected (or made conductive) according to the chip position in the wafer surface. Specifically, in a wafer test process after a wafer process, it requires to write an ID for each chip using a tester or prober.
There is also a known method that prints a mark indicating a chip ID to each chip instead of electrically recording the identification information to PROM. The mark printed to each chip can be visually recognized using an electron microscope. AOKI discloses, in Japanese Unexamined Patent Application Publication No. 2007-243132, a method to print chip IDs to a wiring layer or an interlayer film by preparing multiple masks for forming marks, and repeatedly performing a lithography process using the multiple masks. The method disclosed by AOKI is characterized in that the multiple masks for forming masks include a combination of masks, each with different number of printing chips in one shot. For example, if a first mask capable of printing 16 chips (four rows by four columns), and a second mask capable of printing nine chips (three rows by three columns), are used, unique chip IDs can be provided respectively up to 144 chips (12 rows by 12 columns). The 12 rows (12 columns) is the least common multiple of the four rows (four columns) of the first mask and three rows (three columns) of the second mask.